Distillation apparatus and a method of operating same



Feb. 6, 1962 D, BEDUHN ETAL 3,020,214

DISTILLATION APPARATUS AND A METHOD OF OPERATING SAME Filed NOV. 9, 1956 INVENTORS Daniel E EeMn BYBZMZZE Zfllllfitl? United States Patent Ofiice r 3,020,214 Patented Feb. 6, 1962 3,020,214 DIEaTILLATlON APPARATUS AND A METHOD OF OPERATHNG SAME Daniel E. Beduhn and Richard E. Wernecke, Manitowoc, Wis. Filed Nov. 9, 1956, Ser. No. 621,298 3 Claims. (Cl. 202-481) This invention relates to apparatus for the separation of multi-component mixtures by distillation and a method of operating such apparatus and more particularly to the distillation of mixtures which are subject to severe foaming inside a still. When foam is formed in a still, a portion of the foam may be carried over to the condenser and thus pollute the distillate.

While the present invention is not to be construed as limited thereto, one exemplary mixture which is subject to such severe foaming is the fluid used in commercial dry cleaning processes. This fluid may comprise a mixture containing an organic solvent, a detergent, and water, the solvent and water being immiscible in the absence of the detergent. After this fluid is used it contains impurities such as dirt, oils, greases, etc.

It is then necessary to reclaim the solvent by distillation.

Because the boiling point of the solvent is frequently higher than that of water it is necessary to distill the water along with the solvent. The detergent, having a higher boiling point than either'the solvent or water is not distilled but remains as a residue containing the impurities and can be drained ofi However, because the still must be operated at the boiling point of the solvent, the water in the mixture, if introduced into the still in the usual way, would practically explode into superheated steam With a resultant violent agitation of the mixture and consequent severe foaming.

It is an object of the present invention to provide a still for the effective separation of multi-cornponent fluids.

It is a further object of the present invention to provide a still in which a minimum amount of foam is produced.

An additional object is to provide a still in which no foam will be carried over into the condenser.

Further objects and advantages will become apparent from the following detailed description taken in conjunction with the accompanying drawing in which is shown a sectional elevation of a still provided with a preferred embodiment of the present invention.

The drawing shows a still having a vertical cylindrical tank 19 including a cover 12 secured by any suitable means. The tank lit is provided with a drain 13. A stream inlet pipe 14 passes through a wall of the tank and is divided at a T 16, one branch of which is connected to a steam chest 18 comprising top and bottom plates 20, 22 and connecting side plate 24. Tubes 26 pass through the top and bottom plates 20, 22 to provide liquid passages with additional heating surface. A condensate return pipe 28 provided truth a suitable trap (not shown) serves as an outlet from the steam chest to dispose of condensed steam.

The other branch from T 16 comprises a pipe 30 which is connected to a preheater coil 32 which may comprise a flat spiral (shown in side elevation). A tube 34 leads from coil 32 to a trap outside the tank (not shown) to dispose of condensate in a manner similar to that of the condensate return pipe 28.

A pump 36 drawing from intake line 38 forces the fluid to be distilled through line 40 to an inlet valve 42. The fluid is conveyed from the inlet valve 42 through a pipe 44 to a nozzle or head 46 which is disposed above the coil 32. The head 46 is provided with a series of nozzles or orifices directed toward coil 32. A generally horizontally disposed substantially flat drip plate 48 underlies coil 32. Inlet valve 42 is controlled by a float 49 in response to the level of liquid in the tank 10.

Accordingly, it is believed to be clearly disclosed and described, by the above, that the tank 10 of the still is provided with a first heating zone or surface that is defined by the dripplate 48 and the preheater coil 32; a second heating zone or surface that is defined by the steam chest 18 which is submerged in the liquid being distilled; that the nozzle or head 46 defines structure for discharging the liquid to be distilled into the first heating zone, and that the float 49 and the inlet valve 42 define a sensing device and control for regulating such discharge of liquid in a manner which maintains the liquid level between the first and the second heating zones or surfaces with the second heating zone or surface being submerged therein.

In the upper portion of the tank 10 is located a condenser 50 which comprises a bottom plate 52 lying horizontal in the tank. An inner cylindrical wall 54 rises from bottom plate 52 inwardly of the walls of tank 10 providing a peripheral cooling pocket in which a condensing coil 56 is disposed. The condensing coil 56 may overlying condenser 50 whereby vapors which condense 30' onthe baflle 61 or the cover 12 will drip into the cooling pocket.

From the tank 10, at a point just above condenser bottom plate 52, a condensate outlet pipe 62 leads to a separating tank 64. The separating tank 64 is provided with a foraminous internal baffle 66 to prevent surging. An overflow pipe 68 drains excess liquid from the separating tank 64 and thereby establishes the upper liquid level therein. A second pipe 70 extends upward from near the bottom of the separating tank 64 and serves to drain liquid from the bottom thereof. The pipe 70 may be vented to atmosphere as at 72 to prevent air pockets in the outlet line. It will readily be seen that immiscible liquids in the separating tank 64- can be drawn oif separately. A cooling coil 74 may be provided in the separating tank 64 to finally cool the distillate. Cooling water may be supplied to the cooling coil 74 through a supply pipe 76 and a cooling coil outlet 78 may be connected to condenser inlet pipe 58 since the cooling water is not sufiiciently heated in the separating tank 64 to destroy its usefulness for condensing. In the operation of the still, steam at about 60 lb. gauge pressure, enters inlet pipe 14 and is conducted to the first heating zone or surface of the preheater coil 32 and to the second heating zone or surface of the steam chest 18. The multi-component liquid to be distilled containing water, a solvent and a detergent is forced by pump 36 through inlet valve 42 to the structure defined by the nozzle or head 46 from which it is sprayed onto preheater coil 32 at the first heating zone or surface. Any water contained in the liquid is immediately vaporized upon contact with the preheater coil 32. Since the amount of liquid which is in contact with the preheater coil 32 at any time is small, the amount of foam produced at any time is small and cannot build up to the point where it will be carried over to the condenser.

The remaining liquid falls to the drip plate 48 which, being fiat, holds the liquid only sufliciently that it may become preheated. The liquid then falls to the liquid pool below where it is further heated by the second heating zone or surface of the steam chest 18 and the solvent is vaporized and fiows to the condenser. Since the water has already been evaporated by the preheater coil 32,

the production of'foam in the boiling liquid is minimized. The sensing device and control for the structure which is defined by the float controlled inlet valve 42 serves to prevent the level of the boiling liquid from rising above the preheating coil 32 and thereby prevents fluid containing water from being sprayed into the boiling solvent at the second heating zone or surface.

After; removal of the water and solvent from the liquid only the detergent and impurities remain. This remaining mixture can be drained off by means of drain 13.

While a preferred embodiment of the invention has been described, it is to be understoodthat the invention is capable of other forms and is to be limited only by the scope of the appended claims:

Having thus described the invention we claim:

1. Apparatus for the suppression of foam in the distillation of multi-component liquids comprising a tank, a first heating surface disposed in said tank, said first heating surface including a generally horizontal substantially flat plate immediately underlying a heating coil, structure for discharging a liquid onto said first heating surface, a second heating surface disposed below said first heating surface, said structure being operable by a control which is responsive to a liquid level sensing device located between said heating surfaces, and a condensing surface in communication with the upper portion of said tank.

2. Apparatus for suppressing foam in the distillation of multi-cornponent liquids, said apparatus including, a tank, a first heating zone within said tank defined by a generally horizontally disposed substantially flat plate immediately underlying a heating coil, structure for discharging liquid into said first heating zone, said struc ture being regulated by a liquid level control to maintain, a predetermined liquid level in said tank below said first heating zone, a second heating zone in said tank located below said predetermined liquid level, and a condensing zone in communication with the upper portion of the tank.

3. Apparatus for the suppression of foam in the distillation of multi-componen-t liquids comprising a tank, structure regulated by a control which is responsive to a liquid level in the tank to maintain a predetermined liquid level therein, a first heating surface located above the predetermined liquid level, said first heating surface including a horizontal flat plate immediately underlying a heating coil, a second heating surface located below said liquid level, said structure including a nozzle for spraying liquid onto the first heating surface to enable at least one component of such liquid to be vaporized with the remaining components thereof falling to said liquid level where additional components are vaporized by said second heating surface, and a condensing surface in communication with the upper portion of said tank.

References Cited in the file of this patent UNITED STATES PATENTS 736,240 Erben et al. Aug. 11, 1903 1,253,411 Melchoir Jan. 15, 1918 1,764,190 Bell June 17, 1930 1,913,882 Hells June 13, 1933 1,942,767 Grnan et al. Jan. 9, 1934 2,140,623 Hetzer Dec. 20, 1938 2,289,956 Gans et al. July 14, 1942 2,349,000 Phillips et a1 May 16, 1944 2,479,267 Sanford Aug. 16, 1949 2,609,337 Taylor et al. Sept. 2, 1952 2,649,408 Williamson et a1 Aug. 18, 1953 2,825,680 Stietz Mar. 14, 1958 

1. APPARATUS FOR THE SUPPRESSION OF FOAM IN THE DISTILLATION OF MULTI-COMPONENT LIQUIDS COMPRISING A TANK, A FIRST HEATING SURFACES DISPOSED IN SAID TANK, SAID FIRST HEATING SURFACE INCLUDING A GENERALLY HORIZONTAL SUBSTANTIALLY FLAT PLATE IMMEDIATELY UNDERLYING A HEATING COIL, STRUCTURE FOR DISCHARGING A LIQUID ONTO SAID FIRST HEATING SURFACE, A SECOND HEATING SURFACE DISPOSED BELOW SAID FIRST HEATING SURFACE, SAID STRUCTURE BEING OPERABLE BY A CONTROL WHICH IS RESPONSIVE TO A LIQUID LEVEL SENSING DEVICE LOCATED BETWEEN SAID HEATING SURFACES, AND A CONDENSING SURFACE IN COMMUNICATION WITH THE UPPER PORTION OF SAID TANK. 